1. Field of the Invention
The present invention relates to a circuit module including a circuit substrate in which a plurality of land-shaped mounting electrodes are provided on one main surface.
2. Description of the Related Art
In recent years, further downsizing of mobile terminals has been desired, and further miniaturization and further lowering of heights of circuit modules (high-frequency electronic modules) to be mounted on the mother substrates or the like of mobile terminals has been requested, examples of the circuit modules including a Bluetooth module (registered trademark), a wireless LAN module such as WiFi, and an antenna switch module used for a cellular phone. Such a circuit module includes a circuit substrate where a semiconductor element such as a transistor, an FET, a diode, or an IC or a component such as a resistance element, a capacitor element, or an inductor element is mounted on the front surface of the circuit substrate and a plurality of land-shaped mounting electrodes are formed on the back surface thereof. In addition, since the miniaturization of circuit modules and the lowering of the heights thereof have been requested, the miniaturization of circuit substrates included in the circuit modules has been advanced, and the miniaturization of mounting electrodes formed on the circuit substrates has also been advanced.
With the progress of the miniaturization of mounting electrodes formed on a circuit substrate included in a circuit module in this way, there is a possibility that torsion or a stress is concentrated in a portion on which a mounting electrode in the circuit substrate configuring the circuit module is formed, and a break, a chip, a crack, or the like occurs in the circuit substrate, the torsion being applied to the circuit substrate when the circuit module is mounted on the mother substrate or the like at the time of the assembly of a mobile terminal, the stress being due to an impact or the like occurring, for example, when a mobile terminal has fallen that includes a mother substrate on which the circuit module is mounted via solder or the like.
In addition, the circuit module is repeatedly heated and cooled or an external impact is applied thereto, for example, when the circuit module is mounted on a mother substrate in a mobile terminal or the like and hence, in particular corner portions in the four corners of the circuit substrate may be curved or warped. Therefore, there is a possibility that a mounting electrode is peeled from the circuit substrate. In this way, when a break, a chip, or a crack has occurred in the circuit substrate or a mounting electrode has been peeled from the circuit substrate, a via conductor in the circuit substrate or a transmission line such as a wiring pattern formed within the circuit substrate is damaged, and hence, there is a possibility that a failure of the mobile terminal is caused.
Therefore, so as to prevent a break, a chip, or a crack from occurring in the circuit substrate or a mounting electrode from being peeled from the circuit substrate, it has been proposed that, as for four mounting electrodes formed close to four corners of a circuit substrate, corner portions closest to the four corners of the circuit substrate are cut off and chamfered For example, refer to Japanese Unexamined Patent Application Publication No. 2005-26312, paragraphs [0001] to [0029], FIG. 1, or the like.
In other words, as illustrated in the bottom view of a circuit module of the related art in FIG. 5, in a circuit substrate 501 included in a circuit module 500, from among a plurality of rectangular-shaped mounting electrodes 502 formed on a main surface on a side to be mounted on a mother substrate, as for the four mounting electrodes 502 formed close to the four corners of the circuit substrate 501 and surrounded by dotted lines in the drawing, corners closest to the four corners are subjected to chamfering so that a chamfering amount c becomes a/5 to a/2 (“a” is the length of the shortest side of the mounting electrode 502). Since such a configuration is adopted, a stress applied to the circuit substrate 501 by an external impact such as torsion applied to the circuit substrate 501 is reduced, and a break, a chip, a crack, or the like are prevented from occurring in the circuit substrate 501. In addition, when curves or warps occur in the vicinity of the four corners of the circuit substrate 501 due to the heating or the cooling or the application of the external impact, in particular portions in the mounting electrodes 502, which are close to the four corners of the circuit substrate 501, are prevented from being peeled from the circuit substrate 501.
As illustrated in FIG. 5, as for the four mounting electrodes 502 formed close to the four corners of the circuit substrate 501, corners closest to the four corners of the circuit substrate 501 are subjected to chamfering, and hence, a break, a chip, a crack, or the like are prevented from occurring in the circuit substrate 501 due to the external impact or the mounting electrode 502 is prevented from being peeled due to the circuit substrate 501 being curved. However, the further improvement of the technique has been desired.